Biggest 'aha' moment was that the control box needn't be attached all the time. Set the aperture, disconnect, then shoot - even change lenses, and the f-stop is acknowledged. This, I feel, changes my view on this product. Was a bit underwhelmed, but this workaround (I hear it's very difficult to do this) works well enough for me to go with it.

Wild speculation mode - just need it to power up Image Stabilisation with the 17-55 f2.8 and awesome 24-105 f4.0 lenses for hand-held interviews. Then it's done and I can say goodbye to the EX1s for this kind of work.